A whole-document copy reads its pages off the UI thread, and a copy made
meanwhile (a page selection, a text field's, a comment's, an image) went
to the clipboard first and was then replaced by the document's text.
Any later copy now drops the pending one: copy_selected_text and the
image copies drop it directly, and finish_document_copy, now run at the
end of the frame, drops it when anything else copied that frame.
DocumentCopyJob::of classifies each page from text_failed (a set)
instead of looking it up in pages_without_text's Vec, which was
quadratic in the page count.
SBaksa
3c6be18fb7